Epigallocatechin gallate (EGCG) potentiates the cytotoxicity of rotenone in neuroblastoma SH-SY5Y cells.

Exposure to rotenone, a widely used pesticide, has been suggested to increase the risk of developing Parkinson's disease. Studies indicate that the neurotoxicity of rotenone may be related to its ability to generate reactive oxygen species. The present work was conducted to determine to what extent (-)-epigallocatechin-3-gallate (EGCG), a widely used dietary supplement, modulates the cytotoxicity of rotenone in human neuroblastoma SH-SY5Y cells. Our results indicate that EGCG shows concentration-dependent effects on ROS production and cytotoxicity in SH-SY5Y cells. Treatment of these dopaminergic cells with rotenone (1-50 microM) alone or EGCG (25 or 50 microM) alone caused a significant decrease in cell viability. Pretreatment of SH-SY5Y cells with 25 or 50 microM EGCG potentiated the cytotoxicity of rotenone. The exacerbating effect of EGCG on rotenone toxicity may involve an apoptotic mechanism as shown by the enhancement of caspase-3 activity and activation of other caspases in rotenone-treated SH-SY5Y cells. The potentiating effect of EGCG on rotenone toxicity may be attributed to the enhanced production of intracellular superoxide in SH-SY5Y cells. The enhanced intracellular production of ROS by rotenone-EGCG combination may also account for the increased formation of protein carbonyls in 10,000xg fraction of SH-SY5Y cells detected by anti-HNE antibody. For instance, core histones and nuclear ribonuclear proteins were identified as major putative in vivo targets of HNE. Our present findings indicate that more detailed mechanistic studies are necessary to fully understand the chemistry of EGCG and to justify its use as potentially health-promoting dietary supplement, e.g. in the prevention of neurodegenerative diseases associated with oxidative stress.

Spasmogenic activity and acute toxicity of Yumijangquebo, a herbal laxative formulation.

We evaluated the pharmacological properties and spasmogenic activities of Yumijangquebotrade mark, a Korean herbal laxative formulation. Doses in the range 12-50 microg/ml induced a large spasmogenic effect in isolated guinea pig ileum, similar to that induced by acetylcholine. Pre-treating the tissue with atropine (0.2 microM) completely abolished the contractile effect of Yumijangquebo. The spasmogenic effect of Yumijangquebo and the inhibition of this effect by atropine suggest that a cholinergic mechanism is responsible for its effects. Yumijangquebo increased the gastrointestinal motility in ICR mice at doses between 10 and 37 mg/kg. Yumijangquebo exhibited higher activity than three other laxatives tested, which had activities about 85% of that of Yumijangquebo. In an acute toxicity study using Sprague-Dawley rats, the median lethal dose (LD50) of Yumijangquebo was greater than 2000 mg/kg, and we found no pathological changes in macroscopic examination by necropsy of rats treated with Yumijangquebo. We conclude that Yumijangquebo may be safely used as a herbal spasmogenic laxative agent.

Effects of dietary supplements on induction and inhibition of cytochrome P450s protein expression in rats.

Recent surveys show that 18% of adults in the United States use prescription drugs concurrently with herbal or vitamin dietary products. Despite possible dietary supplement-drug interactions through modulation of cytochrome P450s (CYPs), dietary supplements have not been studied at a screening scale to assess their effects on CYPs. In this study, 116 herbal dietary supplements, commercially available for nutrient supply and weight management, were administered to rats to test whether they modulate the expressions of CYP1A2, 2C11, 2D1, 2E1 and 3A1 proteins. Seventy-five percent of the 116 dietary supplements modulated at least one CYP, while 25% had no effect. CYP2C11 protein expression was the most inhibited by supplements (51%), whereas CYP1A2, 2D1, 2E1 and 3A1 were the least inhibited (12-18%). CYP1A2 was the most induced, modulated by 21% supplements, while CYP2E1 and 3A1 were moderately induced (7-8%). CYP2C11 and 2D1 were not induced by any supplement tested in this study. Thus, this study suggests that dietary supplement-drug interactions may occur through modulation of CYPs in humans when they are taken simultaneously.

Anti-diarrheal and spasmolytic activities and acute toxicity study of Soonkijangquebo, a herbal anti-diarrheal formula.

The anti-diarrheal and spasmolytic activities of Soonkijangquebo (SKJQB), a Korean herbal anti-diarrheal formulation, were subjected to pharmacological evaluation. SKJQB, at a dose of 50-200 mg/kg, inhibited castor oil-induced diarrhea in mice. The median effective dose (ED50) for the anti-diarrheal effect was 93 mg/kg. In isolated rabbit jejunum preparations, SKJQB produced a spasmolytic effect by the relaxation of spontaneous contractions in a dose-dependent manner. The median effective concentration (EC50) for the spasmolytic effect was 3.6 mg/ml. In isolated guinea pig ileum preparations, SKJQB also produced a spasmolytic effect by reduction of acetylcholine-induced contractions. When tested against calcium channel blockade in rabbit jejunum, SKJQB caused a dose-dependent rightward shift in the Ca2+ dose-response curves, similar to that produced by verapamil, a well-known calcium antagonist. In an acute toxicity study in Sprague-Dawley rats, the median lethal dose (LD50) of SKJQB was greater than 2000 mg/kg, and no pathological changes were noticed in macroscopic examination by necropsy of rats treated with SKJQB. Thus, SKJQB may be safely used as a spasmolytic as well as an anti-diarrheal agent.

Induction of the procarcinogen-activating CYP1A2 by a herbal dietary supplement in rats and humans.

Herbal dietary supplements to promote health may be double-edge swords. A herbal dietary supplement, FastOne, which contains extracts of kola nut, grape, green tea and Ginkgo biloba, and is used as an agent for weight management, was administered to rats to test whether it induced CYP1A2, a procarcinogen-activating enzyme. Western blot analysis indicated that treatments with 0.15, 0.3, 0.5, 1 and 2 g/kg of the supplement for 3 days increased CYP1A2 expression in rat liver microsomes in a dose-dependent manner. The 0.3, 0.5, 1 and 2 g/kg treatments increased rat liver microsomal CYP1A2 activity measures as the conversion of caffeine to paraxanthine to 166, 212, 331 and 473% of normal, respectively. In humans, the intake of 2 and 4 capsules of the supplement for 3 days increased CYP1A2 activity to 194 and 203%, respectively, as assessed by the change in the urinary ratio of 1,7-dimethylxanthine plus paraxanthine to unmetabolized caffeine. Intake of the herbal supplement increased CYP1A2 activity to levels higher than that observed from smoking (179%). This study suggests that the long-term intake of the dietary supplement inducing CYP1A2 may increase the incidence of colorectal cancers caused by procarcinogens activated by CYP1A2 in rapid N-acetyltransferase-2 acetylators and of lung adenocarcinoma in slow acetylators.

Prevention of nitric oxide-mediated 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease in mice by tea phenolic epigallocatechin 3-gallate.

In animal models of Parkinson's disease (PD), the toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is mediated by oxidative stress, especially by nitric oxide (NO). Inhibition of NO synthase (NOS) activity in the brain produces a neuroprotective effect against PD induced by MPTP Green tea containing high levels of (-)-epigallocatechin 3-gallate (EGCG) was administered to test whether EGCG attenuates MPTP-induced PD in mice through the inhibition of NOS expression. Both tea and the oral administration of EGCG prevented the loss of tyrosine hydroxylase (TH)-positive cells in the substantia nigra (SN) and of TH activity in the striatum. These treatments also preserved striatal levels of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid (HVA). Both tea and EGCG decreased expressions of nNOS in the substantia nigra. Also tea plus MPTP and EGCG plus MPTP treatments decreased expressions of neuronal NO synthase (nNOS) at the similar levels of EGCG treatment group. Therefore, the preventive effects of tea and EGCG may be explained by the inhibition of nNOS in the substantia nigra.